Late payment from a business in Co. Cork (Eire)

Hi

I was just wondering if the legislation covered interest and debt recovery costs for a debtor in Southern Ireland (Eire). I've looked at the legislation briefly and can see that in general it is regarded as being in the EU, but not part of the UK, but there are areas that state some countries in the EU are also included, but have their own legislation. All of my customers, bar this one are in the UK and I have a standard invoice / 30 day / 60 day and final reminder letters which goes to these. My invoice and letters mention that the legislation will be used. Unfortunately, when the original invoice was sent to the customer in Eire, it was the standard one. As payment is now overdue, should I amend the invoice / letter to NOT include the fees / interest?

Kind regards